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Plastic Micropump using
and Magnetic Membrane
Ferrofluid
Actuation
C. Yamahata and M. A. M. Gijs
Institute of Microelectronics and Microsystems, Swiss Federal Institute of Technology Lausanne (EPFL), 1015 Lausanne, Switzerland
Abstract: The objective of this project is to develop an efficient and low cost pumping device for biochemical analysis
systems, based on magnetic actuation. A rapid prototyping technology is presented to realize two different types of
externally actuated plastic micropumps: (i) an external magnet displaces a ferrofluid liquid plug that plays the role of a piston
in a channel; (ii) an external coil actuates an integrated magnetic membrane, consisting of NdFeB magnetic powder in a
polydimethylsiloxane (PDMS) matrix.
Plastic Microfluidic Chip
A low-cost method for the fast
prototyping of microfluidic chips
has been developed. The
microfluidic chip is a stack of
polymethylmethacrylate
(PMMA) layers. Powder
blasting is used to
realize microchannels,
while complex
structures are machined
with standard milling tools.
In a first step, a metallic mask is realised by laser cutting and applied on
top of a 250 µm thick PMMA sheet. The micropatterning is obtained by the
action of accelerated alumina (Al2O3) particles. The minimum channel
dimensions obtained with this rapid prototyping method is in the 100 µm
range. As an example, a silicone membrane has been integrated to
realize a check-valve. Such valve requires the presence of a PMMA pillar
structure in a cavity; this is machined using standard milling tools. The
quality of the bonding has been verified by applying a fluorescent solution
at 1 bar in the microfluidic structure.
Ferrofluid Micropump
A ferrofluid is a stable colloidal suspension
of nano-sized magnetic particles in a
liquid carrier. In the presence of
an external magnetic field,
the whole fluid responds as
a homogeneous magnetic
liquid. The basic idea of
the ferrofluid micropump is
to generate magnetically a
pressure to pump liquids.
The magnetic liquid plug, which plays the role
of a piston, is externally actuated with a motorized
permanent magnet. The water based ferrofluid
used in the experiments is synthesized in-house
at EPFL. The magnetic saturation of the
ferrofluid is found to be 30 mT at ambient
temperature, which permit larger magnetic forces
than obtainable with most
commercial ferrofluids. Water has been
.
successfully pumped at a flow rate of 30 µL/min without backpressure;
pumping is demonstrated up to a backpressure of 25 mbar.
Magnetic Membrane Micropump
A diaphragm micropump with
2 diffuser elements (dynamic
valves) has been integrated
in a microfluidic plastic
chip. The oscillating
membrane is made of a
polymer magnet and is
actuated with an external coil.
The oscillating diaphragm micropump is
actuated with a 1500 turns coil supplied with a
150 mA alternative current. The micropump
uses 2 diffuser elements. A diffuser is a
constriction element that functions as a dynamic
valve. The numerical simulation of the flow in a
diffuser shows that it has a lower flow resistance
in the positive diffuser …..
direction than in the negative nozzle direction.
Water has been successfully pumped at a flow rate of 400 µL/min
without backpressure; pumping is demonstrated up to a backpressure of
12 mbar.
Christophe Yamahata
[email protected]
EPFL / IMM / LMIS
CH - 1015 Lausanne
Tel: +41 21 693 66 39
Fax: +41 21 693 59 50
Maastricht, January 25-29, MEMS 2004 • Website: http://lmis2.epfl.ch